On an information recording/reproducing apparatus for recording information onto an information recording medium, such as an optical disc, for example, calibration of a recording laser power is performed by an Optimum Power Control (OPC) process according to the type of the optical disc, the type and the recording speed of the information recording/reproducing apparatus, and the like, to thereby set an optimum recording power. This corresponds to variations in recording features of an information recording surface of the optical disc. For example, if the optical disc is inserted or loaded and a command to write is inputted, light intensity is changed sequentially step-by-step, and test writing data is recorded into an OPC area, which is an exclusive test writing area, and a so-called trial writing process is performed. After that, the test writing data recorded in this manner is reproduced. The reproduction result is judged by a predetermined evaluation standard, to thereby set the optimum recording laser power.
More specifically, for example, in the case of a DVD-R, the OPC area is provided with about 400 ECC blocks (clusters), for example, and one ECC block is equivalent to 16 sectors, for example. Here, the “one ECC block” is a management unit on a disc-shaped storage device, and the smallest unit upon error-correcting. In particular, this 1ECC block is about 83 mm long in a track direction, for example, and as described later, it can perform error correction on an about 5 mm defect. On the other hand, the “sector” is the smallest data management unit by pre-format address information in which the record data is error-correctable. Moreover, this one sector is equivalent to 26 sync (or synchronization) frames, and one sync frame (hereinafter referred to as a SF, as occasion demands) is formed from a pre-pit, which is the smallest unit of an address structure. The 4SF is regarded as a unit of the power-step of one OPC process, for example.
Using the unit of the power-step, if the one OPC process is provided with 11 power-steps, for example, the shortest pit length, 2T, and the longest pit length, 8T, of an 8/16 modulated test signal are recorded, with respect to 44SF, with an 11-stage laser power, to thereby perform the OPC process. Namely, 44SF (i.e. about 1.7 sectors) are used for one OPC process. Then, an “OPC pattern”, which is a predetermined pattern including a plurality of test writing recording pits (i.e. OPC pits), is recorded in each power step, with respect to each 4SF.
Therefore, for example, in one disc or one OPC area provided for the one disc, it is possible to perform the OPC process about 3800 times corresponding to the total number of ECC blocks (about 400 ECC blocks).
In addition, there is also disclosed a technology, named as running OPC, of adjusting a recording laser power in real time, in response to the condition of the recording surface where the writing is actually performed, at the time of writing.    Patent document 1: Japanese Patent Publication NO. 3159454    Patent document 2: Japanese Patent Application Laid Open NO. 2002-352517